THERMODYNAMICS AND STRUCTURE OF A DNA TETRAPLEX - A SPECTROSCOPIC AND CALORIMETRIC STUDY OF THE TETRAMOLECULAR COMPLEXES OF D(TG3T) AND D(TG3T2G3T)
THERMODYNAMICS AND STRUCTURE OF A DNA TETRAPLEX - A SPECTROSCOPIC AND CALORIMETRIC STUDY OF THE TETRAMOLECULAR COMPLEXES OF D(TG3T) AND D(TG3T2G3T)
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DOI：
10.1073/pnas.89.18.8832
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发表时间：
1992-09-15
影响因子：
11.1
通讯作者：
BRESLAUER, KJ
中科院分区：
文献类型：
--
作者：
JIN, RZ;GAFFNEY, BL;BRESLAUER, KJ
我们报道了一个DNA四链的热力学和结构的综合表征。用光谱和量热技术证明了在K+存在下，d(TG3T)和d(TG3T2G3T)形成了稳定的四分子络合物。从差示扫描量热测量中，我们得到了在25℃时形成每个四链体的热力学分布如下：-6.9kcal/mol四链体(或-2.3kcal/mol四链体；D(TG3T)四链体的增量-H度=-62.6千卡/摩尔(或四元体的-20.9千卡/摩尔)，D-S度=-186.9卡·K~(-1)·摩尔~(-1)(或四元体的-62.3卡·K~(-1)摩尔~(-1))；D(TG3T2G3T)四链体的增量-G度=-20.2kcal/m ol(或四元体的-3.4kcal/m ol)，D(TG3T_2G3T)四链体的增量-H度=-123.2千卡/摩尔(或四元体的-20.5kcal/m ol)，以及d(TG3T_2G3T)四链体的增量-S度=-346.0卡·K~(-1)·mol~(-1)。这些数据表明，在-25℃时，G-四元体能表现出相当的稳定性，可与大多数Watson-Crick近邻相互作用的稳定性相媲美，甚至超过大多数Watson-Crick近邻相互作用的稳定性，这种稳定性源于非常有利的生成焓。随温度变化的CD测量表明，这两个四链体的熔融温度都表现出异常低的盐依赖性。这种意想不到的行为可能反映了由于结合的K+离子导致的电荷密度降低。对于每个络合物，Na+和K+形式呈现出截然不同的等温和随温度变化的CD轮廓，每个四链结构的K+形式比Na+形式熔化得更快，温度更高。利用一维和二维核磁共振技术，我们证明了d(TG3T)，K+四分子络合物中的链都是平行的，鸟嘌呤糖苷构象都是反的。
We report a combined thermodynamic and structural characterization of a DNA tetraplex. Using spectroscopic and calorimetric techniques, we demonstrate that d(TG3T) and d(TG3T2G3T), in the presence of K+, form stable tetramolecular complexes. From differential scanning calorimetry measurements, we obtain the following thermodynamic profiles for formation of each tetraplex at 25-degrees-C: DELTA-G-degrees = -6.9 kcal/mol of tetraplex (or -2.3 kcal/mol of tetrad; 1 cal = 4.184 J), DELTA-H-degrees = -62.6 kcal/mol of tetraplex (or -20.9 kcal/mol of tetrad), and DELTA-S-degrees = - 186.9 cal.K-1.mol-1 of tetraplex (or -62.3 cal.K-1.mol-1 of tetrad) for the d(TG3T) tetraplex; and DELTA-G-degrees = -20.2 kcal/mol of tetraplex (or -3.4 kcal/mol of tetrad), DELTA-H-degrees = -123.2 kcal/mol of tetraplex (or -20.5 kcal/mol of tetrad), and DELTA-S-degrees = -346.0 cal.K-1.mol-1 of tetraplex (or -57.7 cal.K-1.mol-1 of tetrad) for the d(TG3T2G3T) tetraplex. These data demonstrate that at 25-degrees-C a G-tetrad can exhibit considerable stability, comparable to or even exceeding that of most Watson-Crick nearest-neighbor interactions, with this stability resulting from a very favorable enthalpy of formation. Temperature-dependent CD measurements reveal that the melting temperatures of both tetraplexes exhibit unusually low salt dependences. This unexpected behavior may reflect a diminished charge density due to bound K+ ions. For each complex, the Na+ and K+ forms exhibit drastically different isothermal and temperature-dependent CD profiles, with the K+ forms of each tetraplex melting more sharply and at a higher temperature than the Na+ forms. Using one- and two-dimensional NMR techniques, we show that the strands in the tetramolecular complex of d(TG3T),K+ are all parallel and that the guanine glycosidic conformations are all anti.